Enzyme derivatives

Sulphonated tung oil Enzymes derived from B. subtilis... 

A concentrate of proteolytic enzymes derived from Ananas comosus Merr. proteolytic enzyme (glycoprotein) relative molecular mass = 33000... 

Synthetic resins Acrylic Alkyd. Chiorobenzols Chlorodiphenyls Chloro-naphthalenes Chlorophenols Cumaron Epoxies Melamine formaldehyde Phenol formaldehyde Polyesters Sulphonamide formaldehyde Urea formaldehyde Urethane Vinyl Others Enzymes derived from B. subtilis... 

L-Asparaginase, an enzyme derived from E. coli or Erwinia carotovora, has been employed in cancer chemotherapy where its selectivity depends upon the essential requirement of some tumours for the amino acid L-asparagine. Normal tissues do not require this amino acid and thus the enzyme is administered with the intention of depleting tumour cells of asparagine by converting it to aspartic acid and ammonia. Whilst L-asparaginase showed promise in a variety of experimentally induced tumours, it is only useful in humans for the treatment of acute lymphoblastic leukaemia, although it is sometimes used for myeloid leukaemia. 

The enzyme derived from Pseudomonas sp. strain HI-70 is able to oxidize a wide range of substrates including C12-C15 ketones, C5 and Cg ketones with methyl substituents, and some bicyclic ketones including decalones (Iwaki et al. 2006). 

The acyl-enzyme can eliminate the 4-chlorine atom to generate this reactive intermediate that can then react with a nearby nucleophile such as His57 to give an alkylated acyl-enzyme derivative in which the inhibitor moiety is bound to the enzyme by two covalent bonds (Scheme 11.5). Inhibition is irreversible.59 The mechanism has been confirmed by X-ray structural analysis of protease-isocoumarin complexes. There is a cross-link between the inhibitor and the Serl95 and His57 residues of PPE.60 Human leukocyte elastase is also very efficiently inactivated.61... 

Enzymatic cleaners contain enzymes derived from animals, plants, or microorganisms. Plant and micro-organism-derived enzymes may cause sensitization in many lens wearers [322], A list of commonly used enzymes is provided in Table 10. All of these enzymes are effective in removing deposits from the contact lens surface [323]. They are biochemical catalysts that are specific for catalyzing certain chemical reactions. Those... 

Celik, A., Flitsch, S.L. and Turner, N.J. (2005) Efficient terpene hydroxylation catalysts based upon P450 enzymes derived from actinomycetes. Organic Biomolecular Chemistry, 3, 2930-2934. 

The second development for which IGT is known world-wide is their work on biodesulfurization. The IGT intellectual property package, developed by Kilbane s group, includes two microorganisms, R. rhodochrous strain ATCC 53968 (IGTS8) and B. sphaericus strain ATCC 53969 as well as the enzymes derived from them and cell-free extracts. The biocatalysts and their use were protected in a series of eight patents (plus one US equivalent) and though in some patents a process is claimed, the main emphasis is on biocatalyst. A summary of these patents and the comparison with the early patents of EBC was given in Chapter 3. The patents were entitled ... 

These two strains, B. sphaericus strain ATCC 53969 and R. rhodochrous strain ATCC 53968 discovered by Kilbane as being capable of dibenzothiophene desulfurization were patented as two separate (European) patents [67,91], respectively. These two patents issued by 1991 also described the use of the enzymes derived from these organisms and their cell-free extracts for desulfurization applications. Both strains were reported to carry out selective cleavage of C—S bonds in organic carbonaceous materials. The organism, Bacillus sphaericus strain ATCC 53969, was, however, reported in Exxon patents, to be capable of C—C bond cleavage as well and therefore its ability to perform desulfurization without loss of fuel value is questionable. 

One of the best ways to ensure retention of activity in protein molecules is to avoid doing chemistry at the active center. The active center is that portion of the protein where ligand, antigen, or substrate binding occurs. In simpler terms, the active center (or active site) is that part that has specific interaction with another substance (Means and Feeney, 1971). For the preparation of enzyme derivatives, it is important to protect the site of catalysis where conversion of substrate to product happens. For instance, when working with antibody molecules, it is crucial to stay away from the two antigen binding sites. 

Yet another proteolytic preparation used for debridement of wounds and skin ulcers consists of proteolytic enzymes derived from B. subtilis. The preparation displays broad proteolytic activity and is usually applied several times daily to the wound surface. 

Docosanoids, enzyme-derived docosahexaenoic acid metabolites, were identified initially in the retina 587... 

Interest in immobilized enzyme derivatives stems primarily from our growing awareness of their potential as industrial catalysts and as a new type of model system for the investigation of isolated aspects of complex biological phenomena (l, 2, 3, y. 

Variations in the substrate specificity of enzymes derived from different sources does occur and cross-reactivity should always be checked when developing an enzymic assay. This includes an investigation of the interference from a variety of substances that may be present in the sample in addition to studies on amino acid specificity. 

Some cephalosporins can be both substrates and inhibitors of /3-lactamases. The acyl-enzyme intermediate can undergo either rapid deacylation (Fig. 5.4, Pathway a) or elimination of the leaving group at the 3 -position to yield a second acyl-enzyme derivative (Fig. 5.4, Pathway b), which hydrolyzes very slowly [35][53], Thus, cephalosporins inactivate /3-lactamases by a mechanism similar to that described above for class-II inhibitors. It has been hypothesized that differences in the rate of deacylation of the acyl-enzyme intermediates derive from their different abilities to form H-bonds. A H-bond to NH in Fig. 5.4, Pathway a, may be necessary to assure a catalytically essential conformation of the enzyme, whereas the presence of a H-bond acceptor in Fig. 5.4, Pathway b, may drive the enzyme to an unproductive conformation. The ratio between hydrolysis and elimination, and, consequently, the relative importance of substrate and inhibitor behaviors of cephalosporins, is determined by the nature of the leaving group at C(3 ). An appropriate substitution at C(3 ) of cephalosporins may, therefore, increase the /3-lactamase inhibitory properties and yield potentially better antibiotics [53]. 

It should be noted that some commercial enzyme preparations may contain several enzyme isomers (enzymes derived from one source which belong to the same enzyme class but differ in specificity, stability or other properties). This is most often the case when the commercial preparation was developed for a process industry application rather than a specific chemical biotransformation application. Some fungal enzymes, such as laccase, are sometimes supplied as crude enzyme mixtures. Fungal laccases are manufactured on a huge scale (multitonne per annum) and are principally used in bulk processes such as wood... 

The greatest variety of industrial enzymes are presently derived from microbial sources, with a lesser diversity coming from plant and animal sources 34), Enzymes derived from plant sources and which are used extensively in the food industry include papain, bromelain, ficin, and amylases. Animal enzymes of economic importance include trypsins, lipases, and gastric proteases. 

During infection (1), the virus s coating membrane fuses with the target cell s plasma membrane, and the core of the nucleocapsid enters the cytoplasm (2). In the cytoplasm, the viral RNA is initially transcribed into an RNA/DNA hybrid (3) and then into dsDNA (4). Both of these reactions are catalyzed by reverse transcriptase, an enzyme deriving from the virus. The dsDNA formed is integrated into the host cell genome (5), where it can remain in an inactive state for a long time. 

It has been suggested that the inhibition of ALDH by AGP 17 starts with an interaction between the amino group of 17 and the cysteinyl thiolate side chain of the enzyme to form a modified holoenzyme, or that the enzymic reaction may either proceed through the cyclopropanone 20 yielding 24 a or through the imi-nium ion 18, yielding the modified enzyme 24b [17]. Thus, the covalent he-mithioacetal 24a or hemithioaminal enzyme derivatives 24b rapidly accumulate in the enzyme microenvironment and lead to the observed activity loss, Eq. (9) [21]. 

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